Effective temperature control apparatus



Oct. 5, 1937. c. A. DUNI- IAM ET AL 7 2,094,733 EFFECTIVETEMPERATURE CONTROL APPARATUS Original Filed Jan. 8, 1932 6 Sheets-Sheet l and [7a 30 N H? mm H HUwQ I HM U 5 A Oct. 5, 1937. c. A. DUNHAM ET AL EFFECTIVE TEMPERATURE CONTROL APPARATUS 6 Sheets-Sheet 2 Original Filed Jan. 8, 1952 I'll and

Oct. 5, 1937. c. A. DUNHAM ET AL EFFIEICI'IVE TEMPERATURE CONTROL APPARATUS 6 Sheets-Shet 5 Original Filed Jan. 8, 1932 c. A. DUNHAM ET AL' 2,094,738 EFFECTIVE TEMPERATURE CONTROL APPARATUS Original Filed Jan. 8, 1932 6 Sheets-Sheet 4 (Ya A. @632 [FosZZu/azZ/r Oct. 5, 1937.

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EFFECTIVE TEMPERATURE CONTROL APPARATUS Original Filed Jan 8, 1932 6 Sheets-Sheet 5 svEAI/I M F6?! 951% SUPPLY m [INCREASING I DECREASING AUTOMATIC TEMECONTROL h 5 1 3&1

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C. A. DUNHAM ET AL EFFECTIVE TEMPERATURE CONTROL APPARATUS 6 Sheet-Sheei 6 Original Filed Jan. 8, 1932 rp ysig Rm mmm Patented Oct. 5, 1937 UNITED STATES l ATENT OFFlCE EFFECTIVE TEMPERATUI EE CONTROL APPARATUS Clayton A. Dunham, Glencoe, Ill., and David N.

Crosthwait, Jr., Marshalltown, Iowa, assignors to 0'. A. Dunham Company, Marshalltown, Iowa, a corporation of Iowa Original application January 8, 1932, Serial No. 587,342. Divided and this application March 3, 1934, Serial No. 713,862

4 Claims. (Cl. 237 -9) This invention relates to new and useful improvements in effective temperature heating systems, and more particularly to improved means for automatically controlling a heating-system so that the heat output will maintain a substantially constant condition ofhuman comfort within the building being heated. This application person to experience a. sensation of being chilly.

.At other times, a temperature of 70 Fahrenheit 20 may produce a sensation of being too warm. It

is usual to encounter the first experience when the humidity is low, and the latter when the humidity is high, that is, when the moisture content of the air within the'building is greater.

Human comfort-depends upon the heat dissipation by the skin surface. When the humidity increases, the heat abstractionfrom the skin for a given air movement and temperature decreases, and the sensation of being too. warm results.

comfort is provided by varying the temperature of the inside air with variations in humidity by increasing the rate of heat supply automatically as the humidity decreases, and vice versa. been determined experimentally that there exists certain combinations of temperatures and humidities for agiven air motion which produce the same feeling of comfort or discomfort. These combinations of temperatures and humidities which produce equal conditions of comfort have been charted, and the lines passin'g through these equally effective air conditions are known as equal comfort lines, and. the term effective temperature as used herein is used to indicate heit, and this is called the comfort line.

It has the constant temperature sensation, although the actual dry bulb temperature which produces this sensation will vary as the humidity varies. A maximum number of people will feel comfortable at an effective temperature of 64 Fahren- While at rest in still air, 97 per cent of all people are comfortable at this temperature.

In maintaining effective temperatures, it is essential not to produce chilly sensations, as a result of the absence of radiant heat. This means that heat must be supplied to a building at substantially the same rate the building is losing it, that is so long asheat supply is necessary, this heat should be supplied continually and not intermittently. Also, to maintain the most desirable comfort conditions; the temperature of the air in different parts of the rooms or at various elevations must .be substantially uniform.

The temperatures at the heights of the knee and at the fioor and ceiling should approach the temperature at the breathing line as closely as possible. The foregoing is another way of saying that there must be minimum stratification of the air within the .room or rooms with regard to temperature conditions. This latter condition is best maintained when the heating medium 'which supplies heat to the room does not impart excessive temperatures to the air passing over it in response to convection currents, and this'requirement is best met when the appliance delivering the heat, maintains. temperatures which approach, as closely as is possible, the temperature to be maintained. Excessive heating of the air passing over a steam radiator, for example, causes the temperature at the ceiling to be higher than is the case where the air passing over the radiator is not so highly heated. This conditionis best maintained by utilizing steam at controlled sub-atmospheric pressures as the heating medium, as broadly disclosed in the patents to Clayton A. Dunham, No.- 1,644,114, granted October 4, 1927, and to David N. Crosthwait, Jr.

1,977,303, granted October 16, 1934. The present invention relates to a modification of, and

improvement on, the heating systems therein dis- 1 closed- 7 Obviously, the .most satisfactory result in maintaining equal comfort conditions such as above described are only obtainable when the systemsis completely automatically controlled. According to the present invention, the supplyof steam to the radiators is primarily controlled automatically '1 in response to variations in the pressure ,diiferential between the supply and .dischargesides of the radiators so as to constantly maintain the radiators filled or partially filled with steam at a temperature just sufiicient to replace the heat loss from the building. In addition, thermostatic control mechanism is provided for cooperation with the pressure-control mechanism to insure the restricting of temperature variations within the building within certain predetermined limits.

In addition, humidity responsive mechanism cooperates with the thermostatic control mechanism so as to vary the actual temperature maintained in accordance with variations in humidity so that a substantially constant predetermined effective temperature will be maintained within the building, thus producing approximately constant comfort conditions. In addition, this invention includes various improvements in details of the control mechanism and combinations thereof, whereby these equal comfort conditions are automatically and constantly maintained, or

' varied at different times in the day as circumstances may require or make desirable.

The general object of this invention is to provide an improved heating system for maintaining constant comfort conditions within a building, as briefly described hereinabove and disclosed more in detail in the specifications which follow.

sirable.

Another object is to provide an improved apparatus for proportioning the rate of heat supply to a building so as to maintain effective temperatures.

Another object is to provide an improved combination pressure and temperature actuated control mechanism for a heating system.

Another object is to provide an improved comnism for changing the effective temperatures maintained throughout the day, involving the use of separate day and night thermostats.

Another object is to provide improved apparatus for automatically maintaining temperatures within a building which yield equal comfort conditions to human occupants.

Another object is to provide an improved automatic control ofall of the auxiliaries of a steam heating system in proper sequence so as to supply steam continually'and at as low a temperature as is possible to maintain the desired effective temperature.

Another object is to provide means at a single location for indicating the relative movements of various cooperating parts of the heating system, and means at this location for enabling the operator to manually control the heating system if conditions should require this or make it de- Another object is to provide improved means for controlling the operation of the pump or exhausting mechanism of the sub-atmospheric heating system so as to most effectively cooperate with the other features of the control mechanism. "Other objects and advantages of this invention Will be more apparent from the following detailed In the accompanying drawings:

Fig. 1 is a diagrammatic elevation of a subatmospheric steam heating system with the improved control mechanism applied thereto.

Fig. 2 is a central vertical section through the improved steam-control valve.

Fig. '3 is a partial side elevation of the control valve, looking from the right at the lower portion of the mechanism shown in Fig. 2.

Fig. 4 is a comfort chart illustrating the combinations of dry bulb temperatures and percentages of humidity which corresponds to the effective temperatures.

Fig. 5 is a front elevation of one of the improved thermostats.

Fig. 6 is a front elevation of the thermostat with the cover removed, the thermostatic element being shown in vertical section.

Fig. 7 is a side elevation looking from the right at the apparatus shown in Fig. 6.

Fig. 8 is a vertical section, taken substantially on the line 8--8 of-Fig. 7.

Fig. 9 is a front elevation of the control panel.

Fig. 10 is a wiring diagram of the control panel, the thermostats, the motor mechanism for operating the valve and the pump controlling mechanism.

Reference will first be made to Fig. 1 which shows a heating system of the type with which this improved control mechanism is best adapted to cooperate, although as will be hereinafter apparent the control mechanism may be used with other types of heating systems.

The heating system. here shown is of the subatmospheric steam heating type disclosed in the Crosthwait Patent 1,977,303, hereinabove referred to. This heating system comprises a boiler or generator A from which the steam flows through supply main B and the improved flow control valve G into the portion B of the steam main, from which the radiators D aresupplied. At the outlets of theradiators are steam traps E, F is the return main. G is an accumulator tank for the condensate, the exhausting mechanism is indicated generally at H, and J indicates the differential pressure controller for the exhausting mechanism. At K is indicated generally an electric controlling mechanism for the valve C, at L and L are indicated the improved thermostatic control devices, and M is the improved control panel through which all of the manual and automatic control operations are coordinated, and on which the condition of the different elements of the heating system is indicated.

The reduced pressure steam in main B passes through risers I and inlet valves 2 into the respective radiators D. Suitable orifice plates, such as disclosed in the Dunham patent hereinabove referred to, may be interposed in the respective risers l, preferably between the inlet valves 2 and the radiators for proportioning the steam flows to the respective radiatorsin accordance with the size or condensing capacity and'location thereof. The steam traps E are adapted to close when the radiators are filled with steam and prevent the escape of steam therefrom. When condensate and non-condensable gases accumulate in the radiators, the traps E will open and permit the condensate and noncondensable gases to flow out or to be drawn out by the lower pressure maintained in the return side of the heating system. These gases and the condensate flow through pipes 3 into return main F and thence-through the strainer 4 to equalize the pressures.-

4 into the accumulator tank G. In a similar manner, the condensate and gases accumulating in the portion B of the supply main pass out through float and thermostatic trap into return main F and thence into the accumulator tank, The exhausting mechanism H comprises a separator tank 6 and a pump 1, driven bymotor 8 to withdraw Water from the lower portion of tank 6 and force it through ejector 9 and thence back into the upper part of tank 6, together with the gases and condensate which are withdrawn from accumulator tank G through pipe Ill and check-valve H into the exhauster casing. The gases are vented from separating tank 6 through pipe l2 provided with outwardly opening check valve I3. When a certain amount of liquid has. accumulated in tank 6, a float-controlled mechanism, indicated generally at M, operates to open a normally closed valve 85 so that the pump i can force a part of the liquid out through pipe it provided with check valve l1, and thence throughpipes l8 and i9 into the boiler.

The exhausting mechanism H is operated whenever it is necessary to build up the pressure differential between the supply and discharge sides of the heating system, or whenever it is necessary to transfer accumulated condensate from the accumulator tank G into the separating tank 8. The control mechanism J comprises a diiferential-pressure controller 20 which automatically opens and closes a switch 2| which operates through starter 22 to control the motor 8. The difierential pressure controller comprises a diaphragm subjected on its opposite-sides to the pressures existing in the supply and return sides of the heating system. For this purpose control pipes 23 and 24 extend to surge tanks 25 and 26 positioned in the horizontal section 21 of an equalizing pipe extending between the supply and return sides of the heating system, i 1

the example here shown the relatively high pressure end of pipe 21 communicating through pipe 28 with the supply main B and the'relatively low pressure end communicating through pipe 29 with the return main 1?. A check valve 30 is positioned in the equalizing pipe-21 between the relatively high pressure surge tank 26 and the relatively low pressure surge chamber 25 This valve opens toward the high pressure side of the system and will normally remain closedun less for some reason a lower pressure temporarily exists in the supply main than the pressure in the return main, whereupon valve 30 will open This control mechanism J will operate, in a well known manner, to cause the exhausting mechanism to function whenever the pressure differential between the I supply and discharge sides of the heating system falls below a'predeterminedminimum, and to throw the exhausting mechanism out ofoperation whenever the desired pressure differential has again been established. Also, a fioat-controlled mechanism in the accumulator tank G (disclosed in detail in the .Dunham patent referred to above) acts through switch mechanism 3!] to start the operation of exhausting mechanism H whenever apredetermined amount of condensate has accumulated in the tahk G.

- The improved control valve C will now be described, reierring to Figs. 2 and 3, in addition to Fig. 1. This valve comprises a casing 32, having an internal web 33 separating the high pressure chamber 3% from the relatively low pressure chamber 35. The high pressure chamber 35% is connected with the supply main B leadingfrom means of a plurality of struts i.

the boiler, and relatively low pressure chamber 35 connects with the portion of the supply main B from which the radiators aresupplied with low pressure steam. The web 33 is formed with the aligned valve seats 36 and 31, with which cooperate respectively the connected and substantially balanced valves 38 and 39. Each of the valves 38 and 39 is preferably of the sleeve type here shown, with the slots or openings 39 in the sleeve walls so designed that the tota area of the valve opening will increase by equal increments as the valve is moved upwardly. A removable closure plate Ml permits access to the upper portion of the casing 32. A closure plate, 4| covers the opening in the lower portion of casing 32, this closure plate having an outwardly projecting flange 62 secured to the casing by upper edge with an outwardly extending flange 49. The two casing members 46 and 48. are clamped together at opposite sideswf an'enclosed flexible diaphragm 56 by means, bf a plurality of bolts 50 passing through the flanges A1 and 48 and the peripheral portion of diaphragm 50.

The chamber 5| within the lowercasing member- 48 is open to the atmosphere through central passage 52. The chamber 53 above the diaphragm at is connected through intermediate chamber 54 with an upper chamber 55 from which leads a pipe 56 which extends to-a surge chamber 51 communicating through pipe 58 with the supply main B. The chambers 53, 54 and 55 are all at substantially the same pressure, but the intermediate webs or baiiles '59 are designed to prevent the formation of convection currents in the liquid that accumulates above the diaphragm and thus prevent undue heating of the diaphragm 50 from the steam passing through casing 32. The upper portion 60 of the lower diaphragm casingis supported from the lower portion 48 of the upper diaphragm casing by The lower member 62 of this lower diaphragm casing is clamped to the casing member 60 by means of a plurality of bolts 63 so as to enclose a second flexible diaphragm M similar to the first described diaphragm 50. The chamber 65 above diaphragm 64 is open to the atmosphere through central passage 63. The lower diaphragm chamber ii! is connected through pipe 68 with a surge chamber 69 which in turn is connected through pipe ill with return main F. The surge chambers" 51 and 69 may be conveniently positioned 'adlae cent oneanother and connected by the supportingmember ii, although there is no fluid con-' 5d and is sealed thereto by means of the diaphragm plates "ill and i8 held in place by nuts l9 and 8d. The outer edges of the diaphragm plates'are preferably curved, as indicated at ti,

The lower threaded portion it of stem 12 passes through diaphragmto prevent any cutting action on the diaphragm as itis flexed. The lower end of the stem I2 is screwed into the yoke 82 and locked in ,place by nut 83. A lower valve stem 84 is similarly threaded into the .lower side of yoke 82 and locked in place by nut 85. This valve stem 85 is sealed into the lower diaphragm 64 by means of diaphragm plates 86 and 81 held in place by nuts 88 and 89, in the same manner as the upper valve stem is attached to the upper diaphragm.

A lever 90 is intermediately pivoted at 9| to the lower end of a fulcrum link 92 suspended from lug 93 on the lower diaphragm casing member 48. One end of lever 90 is pivoted at 94 within the yoke 82. The other arm of 1ever 9ll carries a weight 95 suspended by stem 96 and yoke 91 which is adapted to rest in any one of a plurality of notches 98 spaced lengthwise of the longer arm of lever 90. It will be apparent that by adjusting the weight 95 outwardly onthe lever arm 90, the upward pressure exerted on the movable valve assembly will be increased.

A stop crew 40 mounted in the bottom of closure plate 40 limits the upward movement of connected diaphragms 50 and 64 are exposed to atmospheric pressure, but the upper side of the upper diaphragm is subject to the pressure in the supply side of the heating system, whereas the lower side of lower diaphragm 64 is subject to the pressure in the return side of the heating system. Therefore, the net force tending to move the valve assembly downwardly to close the valve is always equal to the pressure differential between the supply and return sids of the system. It will now be apparent that when this downward force exerted by the pressure differential just equals the upward force exerted by the adjustable weight 95, the valves will be in a state of rest or equilibrium. If the pressure differential increases above this fixed normal', there will be a tendency to overcome the efiect of weight 95 and close the valves.- On the other hand, if the pressure differential decreases, the weight 95' will overcome the fluid pressure and open the valves.

In case the valves 38 and 39 'are absolutely balanced, that is of equal size, the device will operate as above described. In case a semi-balanced valve assembly is used, the varying pressure effect may be compensated for by employing other diaphragm. This willchange the effective area of the flexible di'aphragms and compensate for the unbalanced areas of the two-valves.

v unbalanced pressure'due to the difference in elevation between the two diaphragms 50 and 84 may be compensated for by a proper ,variation in the relative sizes of diaphragm plates TI, and 85, 8'I. I

In the general operation of the heating system as thus far described, the desired steam pressure in the boiler A and supply pipe B is obtainedby proper control of the fires beneath :the boiler A,

or by the dampers or otherheat controlling mechanism with which the generator is supplied. The weight is set to respond to a predetermined The- ing mechanism H will now be in operation to lower the pressure in the return main, and this exhausting action will extend throughout the system since the traps E are now open. The traps will remain open until the radiators D are filled with steam, and during this time the exhausting mechanism will be unable to establish any ma terial pressure differential between the supply and return mains. When the steam fills the radiators D and reaches thetraps E, the traps will automatically close, after which the exhausting mechanism H will be able to establish a lower pressure in the return main F than exists in the supply main B, As this pressure difierential reaches the predetermined value, it will act on the diaphragms 50 and 64 to overcome the effect of weight 95 and tend to close the valves 38 and 39, thus throttling the flow of steam to the radiators. As the operation of the valve is gradual, the valve in closing will reach a position where the rate of steam supplied to the radiators is approximate- 'ly equal to the rate of steam consumption or condensation in the radiators, so that the differential will remain substantially constant and the valve will tend to remain in a state of rest or equilibrium in that position for feeding steam to the system at the rate at which it is required. 'If, for any reason, the rate of steam supply should ex- .ceed the desired rate .of heat emission from the will increase and the valve C will tend to close.

The condensing rate of the radiators will then exceed the rate at which steam is being supplied and the supply pressure will drop so that the differential will diminish and the valve C will tend to open again under the influence of weight 95. It will be apparent that any increase in pressure difierential will tend to cause the valve to close and any decrease in the differential will tend to causeit to open, and that the gradual action of the valve in opening and closing between its extreme limits of travel will permit it to reach a position of substantial equilibrium that maintains the steam supply substantially equal to the condensing rate.

It will now be apparent that in view of the fact that the valve C will act to maintain the proper'difierential at all times and that this can only be accomplished when steam is filling the system at the rate that the system is condensing it, theyalve C will act to maintain varying steam with outside temperatures; This will result in the heat emission from the radiators remaining substantially equal to the heat lossfrom the build- I ing.

.It is to be noted that in the construction of the improvedcontrol valve C-no stufling boxes are required. .One side, of each of the movable diaphragms 50 and 64 isflexposedto the atmos-- pressures in the radiating system in accordance phere, whereas the pressure chambers at the aoeavee The constructionand operation thus far described is substantially the same as that disclosed and claimed in the Crosthwait 1 atent 1,977,303, hereinabove referred to.

In addition to the pressure-operated controlling mechanism hereinabove described, thermostatic means is provided for automatically closing the valve or limiting its closing movement in accordance with variations from a predetermined temperature to be maintained throughout the building that is being heated. Furthermore, humidity responsive means is combined with the thermostat so as to vary the standard temperature maintained by the thermostat and its cooperating control mechanism in accordance with variations in the relative humidity of the air within the building so as to maintain a substantially constant effective temperature, that is a constant comfort condition.

The valve C is under the direct control of a motor mechanism indicated generally at K, which is designed to move the valve an amount proportionate to the variation from the standard effective temperature as registered by the thermostatic mechanism L. Referring again to Figs. 1, 2 and 3, an operating lever 99 is intermediately pivoted at I between brackets IOI projecting downwardly from the upper diaphragm casing 48. The inner end I02 of lever 99 is adapt ed to engage a portion of yoke 82 so that down ward movement of this inner arm of lever 99 will positively pull valve stem 12 downwardly to close the valves 38 and 39. However, the inner arm of lever 99 can swing upwardly independently of the yoke 02. In this manner the lever 99 is operable to chose the valves or to limit the amount of their opening movements; but the actual opening movement of the valve isunder the control of the pressure-operated mechanism previously described. A yoke I03 formed at the outer end of lever 99 is pivoted at I04 to a slide block I05 mounted'on the 0 rating" stem I06. A compression spring I01 5 rrounds the stem I06 and is confined between-block I05 and an adjustable nut I00. .At I09 is a stop nut adjustably mountedon the upper end of the stem I06 to limit the upward movement of'block I05. At II04is indicated a small motor assembly which is supported by a .bracket III projecting from the lower portion of the valve assembly. A rotary operating shaft "2 projects. from the motor casing H0 and carries at its outer end a crank arm II3, to which the logi'er end of operating stem I00 is pivotally connected at II4.

.Operating means (hereinafter described) are provided within the casing II0, whereby crank arm II3 will be rotated intermittently, in one direction or the other, an amount proportionate to the variation from a certain predetermined effective temperature as registered by the thermostatic mechanisms L positioned at suitable locations within the building. Thismovement will be transmitted through stern I06 and spring I01 to the operating lever 99, which will impart a reorresponding closing movement to the valves of lever 99 as to limit or restrict the possible opening movement of these valves.

Brief reference will now be made to Fig.4 to explain more ,clearly the effective temperatureswhich the mechanism now about to be describedis designed to establish and maintain. Referring to this -chart, the ordinary dry'bulb temperature readings are indicatedby the vertical lines, and are read on the :horizontal scale 9 and 39, or will so position the inner end I02;

' maintained as well midity in the air are indicated by the lines curving upwardly from the left hand side of the chart. The lines sloping downwardly at approximately 45 from the upper left to the lower right of the chart are the effective temperature lines, that is lines indicating temperature and humidity combinations which will produce sensations of constant comfort to the occupants of the building. The shaded area is known as the comfort zone (any effective temperatures within this zone being considered comfortable by the average human being), and the heavy line passing through the point corresponding to dry bulb and wet bulb readings of 6 4 and 100% humidity is known as the comfort line, the combinations of dry bulb temperatures and humidities corresponding to points on this line profective temperature of, for example, 64, it is.

necessary to vary the ordinary or dry bulb temperature of the air within the building in, accordance with changes in the relative humidity of the air. In other Words, the thermostatic mechanism hereinafter described does not maintain an absolutely standard dry bulb temperature, but varies this standard temperature in accordance with changes in the relative humidity of the air, so as to maintain a constant standard effective temperaturewhich will maintain constant conditions of comfort.

Referring now more particularly to Figs. 5, 6, 7 and 8, thednstrument here disclosed by way of example for maintaining the desired standard effective. temperature aby responding simultaneously to variations in the dry bulb temperature and also to variations in the humidity of the air, will bedescribed in detail. This instrument is not herein specifically claimed, but is distherethrought On cover H6 is mounted an ordinary dry bulb thermometer H8, at the right of which is a scale II9 indicating the dry-bulb 1 temperature, and at the left, a scale I20 indicating the corresponding relative humidity. This thermometer is merely for the benefit of the observer at this location and forms no part of the automatic controlling mechanism. It does indictate the actual temperature that is being humidity.

Referring now to Figs. 6, 7 and 8, a suitable electric resistance'element I2I-, preferably in the form of an exposed resistance coil, isconnected at one end by wire I22 with a binding post I23,

and is connected at the other end by a wire I24 with abinding post I25. A contact member as the actual relative element I2I intermediate the ends thereof, and. is movable to adjust its position on the resistance by mechanism hereinafter described. This movable contact I26 is connected by wire I21 with a binding post I28. The three control wires I29, I30 and I3I (see Fig. 10) extend respectively from the binding posts I28, I23 and I25. It will be noted that the resistance I2I is divided into two effective resistances I2I and I2I", the relative values of which will change, dependent upon the position of movable contact I26 intermediate the ends of resistance I2I. One of these resistances I2I is positioned between two of the circuit wires, such as I29 and I30, and the other resistance I2I" is positioned between the other two circuit wires I29 and I3I. The variations in the relative currents passing through these two circuits (depending upon the relative values of the resistance sections I2I and. I2I") operate through mechanism hereinafter described to cause proportionate movements of the valve-controlling lever 99 in one direction or the other.

The thermostatic element is here shown in the form .of a hermetically sealed casing I32 containing a quantity of temperature responsive fluid I33, one wall of the casing being in the form of a flexible diaphragm or bellows I34. The volume of the fluid I33 will change in accordance with changes in temperature, and the flexible bellows I34 will expand or contract in order to adjust the capacity of vessel I32 to the volume of the heat responsive fluid I33. An operating stem I35 extends from the movable end of bellows I34 and. is provided with a fixed collar I36 engaging one end of a compression spring I31 which abuts at its other end againsta collar I38 on a screw I39 adjustable in a fixed bracket I39. The reduced end portion of stem I35 is slidable in the hollow screw I39.

justing the position of screw I39, the amount the thermostat will move for a given temperature change can be varied. A lever I40 is formed with a yoke I4I which straddles the plunger I35, the

, parent that the thermostat I32, through plunger I35 swings lever I40 about its fulcrum I44 and thus moves contact I26 longitudinally of resistance I2I. By adjusting the fulcrum screw I45, the relative lengths of the upper and lower arms of lever I40 can be changed, thereby adjusting the rate of movement of contact I26 longitudinally of resistance I2I in response to any given temperature'responsive movement at the thermostat.

The humidity responsive mechanism comprisesa long hygroscopic strip or membrane I41 which is anchored at one end I48 to a lever I49 rul- The spring I31 opposes the; movement of the plunger stem I35, and by ad I26 is in constant engagement with the resistance, trip elongating w h increasing humidity n the flexible strip I41 under tension, so that any changes in the length thereof will cause swinging movement of bell-crank I55 about the fulcrum I56. The operative effect of the hygroscopic strip I41 may be varied by turningthe adjusting nut I53.

ThBQICSlSlJZtIiCG element I2I is adjustably mounted on a longitudinally movable rack bar I6I by means of screws I62 adjustable in slots.

I63 in the rack bar. A gear sector I64 meshes with rack bar NH and is pivotally mounted on the base member at I65. The upwardly extending arm I66 of bell-crank I55 is formed with a cam slot I61 in which engages a pin I68 projecting forwardly from the gear sector I64.

It will now be apparent that the contact mem-- ber I26 is moved longitudinally of resistance I2I a distance which is proportional to dry bulb ternperature changes towhich the thermostatic element I32 responds; At the same time, the resistance element I2I is moved bodily, in the direction of its own length, in response to changes in the relative humidity of the air. Assuming, for example, that the air within the building is at a temperature (dry bulb temperature) of 68,

and the relative humidity of the air is 60%. It Will be noted from the comfort chart that this corresponds approximately to a point on the comfort line, that is corresponding to an effective temperature of 64, and if the mechanism is in proper adjustment the contact I 26 should be positioned substantially equi-distant between the two ends of resistance I2I, as shown in the drawings. Assuming now that the temperature of the air should be raised to 72 andthat the 7 relative humidity remains constant at 60%, an effective, temperature of approximately 67 will prevail and it will be desirable to reduce the rate at which heat is imparted to the air by the heating system so as to lower the temperature to the, desired temperature of 68. Under these "circumstances, the resistance I2I does not move, but the contact I26 moves toward the right hand end of the resistance, so as to increase the resistance I2I and decrease the resistance I2I" in proportion to this variation in temperature from the desired effective temperature, and this variationin the values of the resistances I2 I and I 2 I 'f will operate, in the manner hereinafter described, to effect a corresponding and proportionate adjustment of the heating system. Let us now assume that at the same time the temperature increases from 68 to 72, there has been a drop in the relative humidity of the air from 60% to 30%.

It will be noted that a temperature of 72 and a relative humidity of 30% correspond approximately to another point on the 64 effective temperature comfort line, so that under these conditions' there is no reason why there should be any change in the adjustment of the heating system. The parts are so adjusted that this decrease in the relative humidity will cause a contraction of membrane I41 sufllcient to swing the lever' I66 and through cam slot I61 and pin I60 oscillate the gear sector I64 and through rack I6I cause a longitudinal movement of resistance 'I2I to the right justsufiicient to compensate for the movement of contact member I26 so that the re-- sistance and contact -will maintain approximately the same relative positions now shown. If the relative humidity had only dropped to 50%, it will be noted from the comfort chart that the corresponding eifective temperature (with a dry bulb temperature of 72) is approximately 66. The desirability of a decrease in the heat output from the heating system is thus indicated, although not as great a change as would be indicated by a dry bulb temperature of 72 if there had been no change in the original relative humidity of 60%. Accordingly, the resistance I2I is moved a short distance to the right by the hygroscopically responsive mechanism, but not as great a distance as the contact member I26 has been moved, so that there still remains a proportionate change in the two resistance sections I2 I and I 2|" to effect a proper=proportionate adjustment of the heating system. Obviously, if the relative humidity should rise at the same time that the temperature rises, the resistance I2I and contact I26 will be moved in opposite direc tions so as to produce a correspondingly greater increase in the proportionate change of resistances I2I and I2I". It will be noted from a study of the comfort chart that the increments of temperature change are not uniform for equal increments of humidity change. That is, as the humidity decreases, the dry bulb temperature must increase at a more rapid rate, and vice versa. Accordingly, the cam I61 has been provlded, which is so proportioned that the movements of the resistance element I2I will be in proper relation to the movements of the contact member I26 to maintain the desired effective temperature.

In the installation here shown by way of example, two separate thermostats L and L are inabove described, or the night thermostat L'.

may be of a simpler type, designed to respond to changes in temperature only. In fact, both of these thermostats, or the single thermostat, if

only one is used, may omit the hygroscopic control feature as far as certain phases of this invention are concerned, as covered by certain of the claims which follow hereinafter. By employing two separate thermostats Land 1., the

time controlled element may be mounted on the control panel M, thereby avoiding the necessity of incorporating the clock control mechanism in the thermostat itself. On the other hand, a single time controlled thermostat could be used if desired.

It is sometimes desirable to employ a plurality of thermostats positioned .in a plurality of. locations throughout the building, and so coni nected with one another and with the valve controlling mechanism that the heating system will be regulated in response to the average effective temperature registered by all of these thermostatic mechanisms. In such case, each 4 thermostatic mechanism should be modified to embody a pair of separate resistances I 2| and engaging contact members I26, and the several thermostats will be connected in series, all as disclosed and claimed in Patent No. 1,921,172, granted August 8, 1933 to Elbert A. Taylor et a1.

Referring now to the wiring diagram shown in N is indicated the wiring for the pump-control mechanism which-may, if desired, be located adjacent the motor 8 and starter 22.

In the panel board M is mounted a doublethrow triple contact automatic switch 0 which is normally thrown to the right when day thermo 'stat L is in control, but which is'automatically thrown to the left by solenoid I69 in orderto place night thermostat L incontrol of the heating system. The three control wires I29, I39 and I3I leading from thermostat L are connected with the three fixed contacts at the right of switch 0. The corresponding circuit wires I29, I39 and I3I' leading from thermostat L' extend to the corresponding set of fixed contact members at the left of switch 0. At P is indicated a double-throw, triple contact, manually operated switch whereby the heating system may be thrown alternatively from automatic control (by means of thethermostats) to manual control, by means of mechanism. hereinafter described. When switch P is thrown to its upper position, the heating system will be under the automatic control, the three-fixed upper contact members of this switch being connected by wires I19, III and I12 with the three movable contact members of automatic switch 0. From the three movable contact members of switch P extend wires I13, I14 and I15, which lead to the motor mechanism K, wire I14 connecting with the central portion of a solenoid coil I16, and the-two wires I13 and I15 extending respectively to the two ends of this coil. At I 11 is indicated a suitable source of electric power from which leads I18 and I19 extend tothe main line switch I89 positioned on the panel board. From switch I89, wires I8I and I82 lead to the panel light 'switch I83, from which wires I84 and I85 lead to the panel lights I86 and I81 by means of which the mechanism mounted on the panel is illuminated. From the power lines II and I82, wires I88 and I89 lead to the primary I99 of a transformer Q. .The secondary I9I of transformer Q supplies .reduced voltage current through wires I92 and I93 which are ,joined to wires I13 and I15, respectively, of the -trol circuit is completed'from secondary I9I of the transformer Q, this circuit including two parallel branches, one of which branches includes portion I2I of the resistance I2I (in the thermostat L), and also includes one-half of the solenoid coil I16, and the other branch including the'other portion I 2I' of resistance Ill and the 1 other half of solenoid I16. As the relative proportions of the two resistance'sections I2I' and I2'I' are changed, the relative strengths of the two currents flowing. through the two branch circuits and consequently through the two halves of "solenoid coil I 16 will be changed accordingly.

When the strongercurrent is flowing through the.

left hand end of coil I16, the core I94 'of this solenoid will be drawn to the left, and conversely when this end of the coil is the weaker, the core will be drawn to theright. The amplitude of these movements of the solenoid core will be proportional to the variation in the strengths of these two currents flowing through the two halves of the solenoid coil. 'As has been brought out hereinabove, these variations will also be proportional to the variations in one direction or the other from the standard effective temperature for which thermostat L is adjusted.

At I91 and I98 are indicated the fields of two small electric motors, whose armatures I95 and I96, respectively, are mounted on shaft I99 carrying the worm 200 which drives the Worm wheel 20I which is mounted on or geared to the crank shaft II2 (see Fig. 3) which moves the valve operating lever 99. One motor I95 rotates in one direction and the other motor. I96 rotates in the opposite direction. The actuating circuit for the motors I95 and I96 includes a pair of limit switches 202 and 203, hereinafter described, and a reversing switch or balanced relay R mounted in the panel board. The reversing switch R comprises a pair of movable contact members 204,

205 which are moved by the stem 206 connected with the core 201 of solenoid 208. core is moved in one direction, the movable contact members will engage a pair of fixed contacts 209 and 2I0 and when moved in the opposite direction the movable contacts 204 and 205 will engage the fixed contacts 2I I and 2I0, respectively. When solenoid 208 is de-energized the contacts 204 and 205 will assume a neutral position out of engagement with any of the contacts 209, 2 I0 and 2| I. The actuating circuit for motor I95 extends from power lead I18 through main switch I80, wire 2l2, motor field I91, limit switch 202, wire 2I4 to fixed contact 2I0 of reversing switch R, movable contact 204, and wires 2I5, I8I and I19 back to the source of power. In a similar manner, the actuating circuit for motor I96 extends through wire 2I2, field I98, wire 2I6, limit switch 203, wire 2I3 to fixed contact 2 of reversing switch R, thence-through movable contact 204 back to the source of power as before.

At S (in the motor mechanism K) is a proportional control switch actuated from the balanced solenoid I16. An actuating stem 2 I8 connects the movable core I94 of solenoid I16 with the arm 2I9 carrying the movable contact member 220, which may be alternatively moved into engagement with either of the fixed contact members 22l and 222, shown in the form of adjustable screws. All of these parts of the switch S are carried by a supporting plate 223 which is pivoted to swing about the center 224. A bracket 225 extending from plate 223 isformed with a slot 226.

The eccentric disc 221 is pivoted to rotate with worm wheel 20I and carries a movable block 228 from which a pin 229 projects into slot 226. The.

block 228 is adjustable radially of disc 221 by means of screw 230. It will now be apparent that when eccentric disc 221 is rotated in one direction or the other, the switch assembly S will be swungnoid coil 208. Fixed contact 222 of switch S is connected through wire 233, wire I15, and wire When the 234 with the left hand end of soilenoid coil 208.

Assuming now for the moment that the effective temperature at the location of thermostat L rises above the predetermined effective temperature for which the mechanism is adjusted this thermostatic mechanism will operate so as to move the contact member I26 to the right with relation to resistance I2I, a distance which is proportionate to the variation from the predetermined efiective temperature. The relative strength of the resistance section I2I will become greater than that of resistance section I2 I and as a consequence, the strength of the current flowing in the right hand half of solenoid coil I16 will be proportionately greater than that flowing in the left-hand half and the core I94 will be moved to the right so as to swing movable confrom the standard eifective temperature.

The engagement of contacts 220 and 22I of switch S will complete a circuit through the lefthand half of balanced solenoid 208, as follows: From transformer secondary I 9I through wire I92, wire I13, wire 23I', contacts 22I and 220 of switch S, wire 23I, left-hand half of solenoid 208, wire 234, and wire I93 back to the transformer. This will cause solenoid 208 to swing the movable contacts 204 and 205 of switch R into engagement with the fixed contacts 2I I and 2I0, respectively, and will complete the actuating circuit for motor I96, as already described. This motor will now rotate the worm' 200 and worm wheel 20I, causing a movement of shaft H2 and. crank arm H3 in such a direction as to lower the left hand end of lever 99 (Fig. 2) and partially close the valves 38 and 39, or limit the possible opening movement of these valves in case the valves have already been closed by the pressureoperating mechanism. At the same time, the eccentric disc 221 will be rotated slowly in a clockwise direction, this movement causing pin 229 which engages in slot 226 to swing the switch assembly S to the right until contact 22I isdisengaged from contact 220, thus breaking the circuit through balanced solenoid or relay 208, which is so constructed that it will automatically return to neutral position and break the motor circuit, thus stopping the motor I96. The arcuate extent of this swinging movement of switch bracket 223, and consequently the time during which motor I96.will operate and the distance through which the valves will be moved, will depend upon the arcuate distance through which contact member 220 has been moved by means of the balanced solenoid I16, which in turn is proportionate to the variation in temperature from the desired standard. It will thus be seen that the valves 38 and 39 will be closed an amount proportionate to the temperature variation above the desired standard effective temperature. In

. an exactly analogous manner, in case the effective temperature falls below the desired standard, contact I26 will be moved to the left, thus causing movable switch member 2I9 to close the circuit through contacts 220 and 222 of switch S, which will result in motor I95 being energized to rotate the valve operating mechanism in the oppositedirection and open the valves, or rather permit them to be opened by the operation of the pressure-diaphragms. In this case, the eccentric disc 221 will be rotated in 'a counter-clockwise direction so as to swing the switch bracket 223 to the 75 left until contact 222 is disengaged from movable contact 220. Y J

By adjusting the pin 229 radially of disc 221, the distance through which the valves will be moved in proportion to any temperature variation can be adjusted. 'In case pin 229 is positioned substantially coaxial with disc 221, it will be noted that no swinging movement of switch assembly S will result from the rotation of the eccentric disc. In such case, the motor I95 or I96, as the case may he, would continue to rotate indefinitely, or until the movable contact 220 is returned to its central position. For this reason the limit switches 202 and 203 are provided.

'In the example here shown, each of these limit,

switches comprises a fixed contact 235 and a movable contact 236 carried by one arm 231 of a switch lever pivoted centrally at 238. A pairmoved from switch arm 240, the contact 236 swings back into engagement with fixed contact 235.

The above discussion has assumed that switch 0 was thrown to the right so that the system was under the control of the day thermostat L. If switch 0 is thrown to the left, the system will be controlled in exactly the same mannenby the night thermostat L which is, however, adjusted to maintain a lower temperature. The automatic switch 0 is under the control of the time-controlled mechanism indicated generally at T. The detailed construction of this timecontrolled mechanism is not a part of this invention, the apparatus used being of the type in which the quick-acting switch-24! 'is operated directly from the clock mechanism and is closed at a certain hour to throw the thermostat L' into control, and is opened in the morning to again place thermostat L in control. The switch 242 is automatically closed at periodicintervals to energize the motor 243 to rewind the clock. When switch 24I is closed by the clock mechanism, a circuit is completed between the two power-lines I88. and I89 as follows: Through wire 244, magnet coil I69 of switch 0, wire 245 to the switch 24!, and wire 246 to power line I89. The energization of magnet I69 throws switch 0 to the left so as to place the night thermostat in control.

If manually operated switch P is thrown from its upper to its lower position, the automatic con trol by mearisfof the thermostats is thrown out of service, and the heating system may nowbe controlled manually by means of theapparatus indicated generally at V. This comprises a fixed resistance 241 which corresponds to the resistance I2I in the thermostat L. A movable contact 248 engages this resistance intermediate its ends, the contact member being carried by a pointer 249 pivotally mounted at its lower end 250. The pointer is operable by a knob I positioned on the face of the panel board M, and the upper end of the pointer indicates the resulting position of the valves on the dial or scale indicated at 252 (see Fig. 9). The movable contact 248 is connected by wire 253with the lower central contact of switch P, and the two lower outside contacts of this switch are connected by wires 254 and 255 with the respective ends of resistance 241. By

manually moving the contact 248 by turning knob 25I, the relative proportions of the two sections into whichresistance 241 is divided will control the heating system in exactly the same manner as described in connection with the automatic operation of the thermostats L and L. The wires 253,254 and 255 simply take the place, in the control circuit first described, 01 the wires I29, I and I3I. I

The temperature indicator W on the panel board comprises a balanced solenoid 256 which is connected in parallel, through wires 251, 258 and 259 with the balanced solenoid I16 which operates the proportioning switch S. The core of this solenoid 256 operates, through plunger 260, a pointer 26'I, which indicates the room temerature on a dial orscale 262.

A pair of signal lights 263 and 264 on the control panel M indicate at any moment whether the steam supply is being increased or decreased. One side of each of these lightsis connected through wire 265 with the power line I99. The other side of light 263 is connected through wire 266 with the fixed contact 2I0 of switch R, and

:q the other light 264 is connected through wire 261 with the fixed contact 2| I of switch R. The movable contact 204 of switch R completes the circuit through one signal light or the other, depending on whether it is in engagement with fixed contact 2 or fixed contact 2I0.

It will be noted that the constantly burning illuminating lights I I06 and I 81 (already described) are not indicated in Fig. 9, since indirect lightingof the panel board is used. However,-

The motor 8 which drives the pump 1 is directly 5 controlled through the mechanism indicated at N in Fig. 10, which, as alreadystated,-may be positioned adjacent the motor. The pump is also controlled through a series of mechanismsmounted on the panel board M, among which is a switch X by means of which the automatic control of the pump can be thrown out of service and a manual control substituted; 9. switch Y which determines whether or not the time-controlled mechanism shall effect the operation of the pump, and a quick-acting relay Z. The pump motor and the controlling devices therefor do not receive their power from the same power source I11 from which the mechanisms previously described are energized, but from aseparate source of current, here indicated by the three alternating current power lines 268, 269 and 210 (see lower left hand corner of Fig. 10) At 2' are indicated the terminals of a three-phase alternating current motor 8 or the starter therefor. At 212 is indicated a three-pole switch which is normally open to stop the motor, but which may be closed to start the motor by means of the electromagnet 213. At 214 is indicated a thermal overload relay which is normally closed and is in circuit with the actuating magnet 213. In case of an excessive current or overload, this switch 214 will open in well known manner so as to break the motor circuit. Whenever switch 3| is closed (this switch being controlled by a float in the accumulator tank G, as already described) a circuit will be completed through one phase of the alternating current circuit as follows: From wire 268 through wire 215, switch 3|, wire 216, magnet 213, and thermal switch 214 to the power line 269. In this manner the motor will be started to operate the exhausting mechanism whenever a suflicient quantity of condensate has collected in the accumulator tank G, and the motor will be stopped whenever this condensate has been withdrawn into the separating tank 6 since the switch 3| will then open and de-energize magnet 213. The switch 3| is in control of the pump motor inthe above described manner at all times, regardless of the positioning of the several mechanisms on the panel'board, as hereinafter described.

Wires 211 and 218, through which this same energizing circuit for magnet 213 may also be completed, extend respectively to the terminals 219 and 288 of an automatic switch 28| positioned on the panel board. This switch 28| is normally closed so as to extend the circuit to terminals 282 and 283 from which wires 284 and 235 extend, respectively, to the two fixed contacts 288 and 281 of the relay Z. The movable contact plate 288 of this relay may be moved up to close the circuit through contacts 286 and 281 by means of the magnet device indicated at 289. Whenever the relay 2 is closed in this manner, the circuit will be completed through wires 211 and 218 so as to energize magnet 213 and close switch 212, thus starting the motor 8.

The energizing circuit for magnet 289 which closes the relay Z includes the switch 2| of differential-pressure controller J, one side of which is connected through wire 298 with the central power lead 289, and the other side of which is con nected through wire 29| with terminal 292 of the relay device. A wire 293 extends from this terminal to the magnet 289. It will thus be apparent that whenever the necessary pressure difl'erential has been established, and switch 2| has consequently been opened, the magnet 289 will be deenergized, and consequently the pump motor will cease to operate.

When the automatic control of the pump motor is in effect, the switch X will be closed, at which time the actuating circuit for magnet 289 will extend from this magnet through wire 294, terminal 295, wire 296, through one arm of switch X, wire 291 to the movable contact 285 of switch R, fixed contact 289, wire 298,'central arm of switch X, wire 299, terminal 388, and wire 38| to fixed contact 281 of relay Z, thence back through Wires 285 and 211 to the power lead 268, thus completing the energizing circuit for magnet 289 through one phase of the alternating current circuit whenever differential-controller switch 2| is closed and the switch R is moved to the right, which latter will occur when the valve is adjusted for increasing the steam supply.

The energization of magnet 289 will close the movable contact 288 of relay Z against the fixed contacts 288 and 281 and result in the closing of switch 212 and the starting of the ,pump motor. A holding circuit, will now be completed through magnet 289 which will hold the relay closed even though the movable contact 2850! switch R moves away from the fixed contact 289. Thisholding circuit extends from magnet 289 through wire 294, resistance 382 which cuts down the current flowing through this shunt circuit, and wire 383 to fixed contact 288 of relay Z, movable contact-288. fixed contact 281 and thence as in the original circuit. This circuit will remain complete and the pump will continue in operation until the pressure difl'erential has been established and switch 2| is opened, or until the desired effective temperature has been established, atwhich time the energizing circuit for magnet 239 is short-circuited,' by means of the temperature-indicator W. The pointer 2 or this temperature indicator carries a contact 385 will occur at a higher temperature for decreasing humidities and at a lower temperature for increasing humidities. This is because the pointer 28| will actually read somewhat highwhen the humidity is decreasing, and low when the humidity is increasing, although the reading will be accurate when conditions become stabilized. The construction of this humidity compensator 389 may be similar to that already described in connection with the thermostat L, or any other suitable form. When the effective temperature has been raised to such a point that contact 384 engages contact 385, a shunt circuit about the magnet 289 is established as follows: From terminal 292 through wire 3|8, resistance 3, wire 3|2, terminal 3|3, wire 3|4, switch X, wire 3|5, contacts 395 and 384 of temperature indicator W, wire 3|6, switch X, wire 298 and thence as in the previously described circuit. The completion of this circuit will short circuit magnet 289 and cause the relay Z to open, whereupon the pump motor will stop.

It is sometimes desirable in the interest of economy, or for some other reason, to have the differential-pressure control and thermostatic control of the pump continue only in the day time, but be thrown out of service at night, at which time the pump is only started by means of switch 3| when suflicient condensate has accumulated in the tank G. In order to bring about this operation, the switch X remains closed, but

switch Y is thrown to its lower position so that, as indicated on. the panel board M, the pumptime control is in force. The normally closed switch 28| is automatically opened whenever the will be simultaneously energized to open the switch 28I, thus breaking the automatic control circuits for the pump. It will be noted that when switch Y is in its upper position (so as to throw out the time-control of the pump) a shunt circuit is formed around the automatic switch 28| through wires 32|, 322, switch Y and wires 323 and 324. Thus, even though switch 28| is opened as the result of the time mechanism'T, throwing the thermostat L' into service, the pump control circuits will still remain complete.

It switch X is opened so as to throw the automatic pump control out of operation, the pump motor can still be stopped and started manually by means of the push-button switches 324 and 325, that is, providing the pressure diflerential has not been established and switch 2| at the differential controller is closed. The switch 324 completes a shunt circuit between wires 288 and 289 so as to temporarily establish the same circuit that is automatically closed by the engagement of moveable contact 285 of switch It with fixed contact 288. This will cause magnet 238 to be ones.

temperature and gized and close the relayZ and since a holding circuit for this magnet is immediately completed, as already described, the closing of push button switch. 324 need only be momentary. The stopping switch 325 is connected between the wires; 296 and 3 so as to momentarily complete the same short-circuiting circuit that is automatically closed by the pointer 26l of temperature indicator W.

Referring now briefly to the general operation of this heating system, the production of steam at the generator A will be so regulated by'means of suitable damper or burner controls, as to supply steam at substantially the proper sub-atmospheric pressure to replace heat lost from the buil ng. The pressure-operated controller C will respond to variations in the pressure differential between the supply and return sides of the system so as to maintain the radiators D filled or partially filled with steam at a pressure approximately sufficient to replace these heat losses. In addition to this differential pressure control and in direct cooperation therewith is the automatic idity control mechanism whereby a subst ntially constant effective temperature is maintained in the building being heated. The greater part of the manually operable devices for regulating the heating system, and the apparatus for indicating the condition of the heating system, are centralized on the panel board M which may b ositioned in any convenient lo,- cation. In case fully automatic control of the heating system is to be maintained throughout the day and night, the several switches are positioned as shown in Fig. 9. Switch P is thrown up so as to place the automatic temperature control system in service. Switch X is also thrown up to insure automatic .control of the pump. Switch Y is thrown up so as to put the time-control of the pump out of service, that is the pump..-

will be automatically controlled by the differential controller and thermostat at night, as well as by day, By'a suitable adjustmentof the time con-' troller T, the system will be thrown from the con-- trol of the day thermostat L to the control of the night thermosat L at a determined hour in the evening, and will be returned to the control of the day thermostat L at a certain hour in the morning. Under these conditions, whenever the efiective temperature at the location of thermostat L (or L) exceeds the predetermined standard efiective temperature for which thethermostat is adjusted, or. the average effective temperature throughout the building exceeds the standard temperature in case a plurality of thermostats are used, this thermostatic mechanism will cause the electrically operated mechanism K to partially close the valve C and cut down the flow of steam to the radiators. The valve G willstill be under the control of the differential-pressure operating mechanism, but the maximum opening of the valve C willbe limited by the position of control lever 99, which is determined by the action of the thermostatic mechanism. In case the effective temperature fallsbelow the desired standard, lever 99 willbe automatically adjusted so as to permit a wider opening of the control valve C, and this opening of theval've'will be effected by the differential-pressure control mechanism at such a rate as to maintain the proper eflicient supply of steam to the radiators. If .the steam supply is being increased at any time, this will be indicated by the signal light 263 onthe panel board, and if the steam supply is being decreased, the light 264 will be lighted. The room temperature existing at the thermostat or thermostats is indicated by the mechanism W on the panel board. At the same time, the pump motor is being automatically controlled so as to maintain the necessary pressure-differential between the supply and discharge sides of the radiators. Whenever this pressure differential has been established, the pump will be stopped by the opening of switch 2|, no matter what the positioning of the other control apparatus may be. In the interest of economy, the pump will be automatically stopped whenever the effective temperature, as registered by the thermostats, has been raised to such a point that the temperature indicator W will close the switchat contacts, 3E4 and 305. At such times,

M the supply of steam is being cut down and the functioning of the pump is temporarily unnecessary. However, as soon as the'thermostats indicate the need for an increase of the steam supply, the switch R. will close the control circuit at 205, 209 so that the pump can again operate, in case the necessary pressure differential is no longer established and the switch 2| is closed. In any event,'the pump can be started in operation at any time by the closing of switch 3| in order to remove an excess of condensate from the accumulator tank G.

In case it is desired to discontinue the differential-pressure control of the pump at night, the switch Y is thrown to its lower position, whereupon the pump will be automatically controlled as above described during the day time,'but at night will only be operated when necessary to remove condensate irom the accumulator tank. By

control mechanism out of service and control the system manually, the switch P is thrown to its lower position. The operator can then control the system to increase or decrease the possible opening of valve C and thus regulate the steam supply by turning the knob 25! on the panel board, the positioning of the valve being indicated on the scale 252.

The entire electrical temperature control sys-" ,whenever a suflicient quantity of condensate has accumulated in tank G so as to remove this condensate and at the same time, incidentally, somewhat lower the pressure in the return main F. Since the exhausting mechanism is not in operation a suficient portion of the time to maintain the pressure differential, the valve C will remain open and steam from generator A can flow continuously into the radiators.

Since the thermostat L is adjusted to automatically maintain eifective" temperatures, it will be apparent that the dry-bulb temperature indicated by thermometer 8 on the scale H9 corresponds to a known relative humidity and that the prevailing relative humidity can consequently be read directly on the scale I20 at the left. This is a simple and convenient means for indicatin the relative humidity so that suitable steps can .be taken to correct the humidity if it is too low.

While the mechanism hereinabove disclosed by way of example is especially designed for use with a heating system utilizing steam at sub-atmospheric pressures, it will be apparent that the invention, in its broader aspects, relates to a system of maintaining effective temperatures in accordance with changes both in the temperature and the humidity of the air, and can be applied to other types of heating systems, such as those utilizing steam at super-atmospheric pressures, or hot water, as a heating medium. The invention discloses a, system of air-conditioning wherein, instead of attempting to regulate the actual humidity of the air, the dry-bulb temperature is varied inverselywi-th changes in the humidity. From this broad viewpoint,. the actual heating medium used is of secondary importance.

We claim:

'1, A steam heating system comprisinga radiator, a steam. supply conduit leading thereto, a steam control valve in this conduit, a discharge conduit leading from the radiator, a steam trap in the discharge conduit, an exhausting mechanism for lowering the pressure in the d'scharge ccnduit and removing condensate, a motor for driving the exhausting mechanism, means for adjusting the steam control valve, means for starting the motor whenever the pressure differential between the supply and discharge conduits falls below a predetermined standard and the valve is adjusted to increase the supply of steam'to the radiator and for stopping the motor when the pressure difierential has been established, and means automatically actuated whenever the valve is adjusted to decrease the supply of steam to the radiator for stopping the motor regardless of the condition of the pressure differential.

2. 'Asteam heating system comprisingaradiator, a steam supply conduit leading thereto, a steam control valve in this conduit, a discharge conduit is broken, a switch in the circuit, means for closing the switch whenever the pressure differential between the supply and discharge conduits falls below a predetermined standard and for opening the switch when the pressure differential is established, a, second switch in the circuit, means for closing this switch whenever the valve has been adjusted for increasing the steam supply and for opening the switch Whenever the valve is adjusted for decreasing the steam supply, and means for breaking the circuit whenever a predetermined temperature is established in the space being heated.

3. A steam heating system comprising a radiator, a steam supply conduit leading thereto, a steam control valve in this conduit, a discharge conduit leading from the radiator, a steam trap in the discharge conduit, an exhausting mechanism for lowering the pressure in the discharge conduit and removing condensate, a motor for driving the exhausting mechanism, means for adjusting the steam control valve, a control circuit for the motor whereby the motor is started when the circuit is completed and stopped when the circuit is broken, a switch in the circuit, means for closing the switch whenever the pressure differential between the supply and discharge conduits falls below a predetermined standard and for opening the switch when the pressure differential is established, a second switch in the circuit, means for closing this switch 4. Temperature controlling apparatus for a heating system, comprising a radiating system, a supply valve for determining the flow of heating medium to the radiating system, a thermostatically and hygroscopically controlled device positioned at a location remote from the valve and comprising balancing resistances which are prov portionately varied in response to variations from a predetermined effective temperature, motor mechanism for proportionately adjusting the size of the valve opening, and control circuits including the resistances for determining the direction and amount of rotation of the motor mechanism in accordance with the variations from the predetermined effective temperature at the remote 10-? cation; CLAYTON A. DUNHAM.

DAVID N. CROSTHWAIT, JR. 

